the microflora of eagle island mangrove swamp, southern...

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The microflora of Eagle Island mangrove swamp, southern Nigeria

Keywords: Mangrove swamp, microbial ecology, rhizosphere.

ABSTRACT: The occurrence, abundance and distribution of bacteria (nitrifying, nitrogen-fixing and heterotrophic), yeasts, moulds, algae and actinomycetes in mangrove and freshwater swamps were studied. Microbial abundance and diversity were greater in freshwater than in mangrove swamps. Actinomycetes were the dominant organisms in sediments while algae occurred widely in water. A total of 57 microbial genera were isolated from the mangrove swamp, out of which the algae had greatest diversity comprising 20 genera. It was followed by the moulds, which had 16 genera, then bacteria (10 genera), yeast (6 genera) and actinomycetes (5 genera). The organisms were widely distributed in all parts of the swamp, though actinomycetes did not occur in the water samples and yeasts occurred sparsely in freshwater. The study implicates the genera Aeromonas, Proteus, Serratia and Citrobacter (bacteria); Thermoactinomyces and Streptomyces (actinomycetes); Aspergillus, Trichoderma, Penicillium, Mucor, Fusarium, Geotrichum, Verticillium and Botrytis (moulds); Rhodospiridium, Trigonopsis and Pichia (yeasts); Gomphonema, Fischerella, Asterionella, Borgea, Nostoc, Chlamydomonas, Laminaria, Spirulina, Chlorobotrys and Vaucheria (algae) as autochthonous members of the mangrove swamps of the Niger delta. Mangrove swamps therefore harbour a wide range of microorganisms some of which are indigenous to this slightly acidic habitat and occur in varying proportions.

602-616 | JRB | 2012 | Vol 2 | No 6

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www.jresearchbiology.com

Authors:

Okpokwasili GC1,

Ifenwanta CE1 and

Nweke CO1,2.

Institution:

1. Department of

Microbiology, University of

Port Harcourt, P.M.B.5323,

Port Harcourt, Nigeria.

2. Department of

Microbiology, Federal

University of Technology,

P.M.B. 1526, Owerri,

Nigeria.

Corresponding author:

Okpokwasili GC.

Email:

[email protected]

Web Address: http://jresearchbiology.com/documents/RA0241.pdf.

Dates: Received: 14 May 2012 Accepted: 01 Jun 2012 Published: 22 Sep 2012

Article Citation: Okpokwasili GC, Ifenwanta CE and Nweke CO. The microflora of Eagle Island mangrove swamp, southern Nigeria. Journal of Research in Biology (2012) 2(6): 602-616

Journal of Research in Biology

Original Research

Journal of Research in Biology

An International

Scientific Research Journal

An International Scientific Research Journal

INTRODUCTION

Mangroves are woody plants that grow at

the interface between land and sea in tropical and

sub-tropical latitudes. These plants, and the associated

microbes, plants, and animals, constitute the mangrove

forest community or mangal. The mangal and its

associated abiotic factors constitute the mangrove

ecosystem (Kathiresan and Bingham, 2001). The plants

refer to evergreen salt-tolerant species of shoreline trees

and shrubs belonging to numerous unrelated families that

share similar habitat preferences, physiognomy,

physiology and structural adaptations (Kinako, 1977).

Mangrove ecosystems cover roughly 60-75% of

the world’s tropical and subtropical coastlines

(Holguin et al., 2001). The coastal region of Nigeria is

dominated by swamp forests of which mangrove swamps

cover a sizeable proportion. The mangrove swamp zone

lies between latitude 4.0 and 7.6°N and is made up of

three subzones i.e. the freshwater, saltwater and

brackishwater swamps. In southern Nigeria, they consist

of an area of low-lying land bordering the coastal

swamps and creek area (Onofeghara, 1990). The Eagle

Island houses one of the mangrove swamps of the Niger

Delta. It is inundated by saltwater for 2-10 months in a

year (Onofeghara, 1990). The swamp is extensively

covering a wide area of land occupied chiefly by

mangrove plants.

Mangrove communities are highly productive

ecosystems that provide large quantities of detrital

organic matter to nearby coastal waters. The detritus

serve as a nutrient source and constitutes the base of an

extensive food web involving many organisms of

commercial importance. Basically, microbes are

responsible for nutrient transformations within mangrove

ecosystem (Alongi et al., 1993). In tropical mangrove,

bacteria and fungi constitute 91% of the total microbial

biomass while algae and protozoa represent only 7 and

2% respectively (Alongi, 1988). In temperate, intertidal

surface sediments, algae are the dominant contributors to

total microbial biomass and usually account for 1-2% of

total sediment organic carbon (Rublee, 1982).

In the other parts of the world, the microbial

productivity and diversity have been widely studied and

documented. The microbial ecology of Australian

mangrove ecosystem has been widely investigated by

Alongi and co-workers (Alongi, 1988; Alongi et al.,

1993). Kathiresan (2000) has reviewed studies on the

microbial composition of Pichavaram mangrove,

southeast India. However, little is known about the

ecology of microorganisms in Nigerian mangrove

ecosystems. Literature on the microbial ecology of Eagle

Island mangrove ecosystem is even scantier. Available

publication have been on the phytoplankton flora of the

Warri-Forcadoes estuaries (Opute 1990, 1991), lower

reaches of the Nun river (Yakubu et al., 1998),

epipsammic and epipellic algae of Qua Iboe River

estuary (Ubom and Essien, 2003; Essien and Ubom,

2003; Essien et al., 2008) and the density of hydrocarbon

utilizing bacteria in Iko River mangrove ecosystem

(Udotong et al., 2008). Not much is known on the

microflora of Eagle Island mangrove ecosystem.

This study therefore presents the composition, abundance

and distribution of the microbial community of

Eagle Island mangrove swamp.

MATERIALS AND METHODS

Study area

All samples were collected from the Eagle Island

located behind the Rivers State University of Science

and Technology, Nkpolu, Port Harcourt, Nigeria. Like

the other mangrove swamps of the Niger Delta, it lies

between Latitude 4 and 7.6° North. The swamp is

extensive, covering a wide area of land with a top layer

of mud slurry overlying a relatively hard substratum.

It is dominated with mangrove vegetation and conforms

to the characteristics of mangrove swamps.

Collection of samples

The soil samples were collected from the

Okpokwasili et al.,2012

603 Journal of Research in Biology (2012) 2(6): 602-616

rhizosphere and non-rhizosphere areas. Soils from these

areas were dug up using sterile hand trowel and collected

in sterile bags. The sediment samples were collected

using a sediment grab. The water samples were collected

in sterile screw cap bottles. All samples were taken to the

laboratory in a cooler and analyzed within six hours of

collection.

Enumeration and isolation of microorganisms

Ten-fold serial dilutions of the water, sediment

and soil samples were prepared in sterile 0.85%

NaCl solution. Small aliquots (0.1 ml) of water and

suspensions of soil and sediment were aseptically

spread-inoculated onto triplicate plates of different

microbiological media and incubated at room

temperature (28 ± 2°C). The fungal populations were

enumerated on Sabouraud dextrose agar (Difco)

supplemented with streptomycin at 50 μg/ml to suppress

bacterial growth. Incubation was at room temperature for

48 h and five days for yeasts and moulds respectively.

The hererotrophic bacterial population was enumerated

on nutrient agar plates after 48 h incubation. Nitrifying

and nitrogen-fixing bacteria were enumerated on

Winogradsky medium of Colwell and Zambruski (1972)

and the Azotobacter medium of Krieg (1981)

respectively following four days of incubation.

Actinomycetes were enumerated on starch-casein agar

(APHA, 1985) following seven days of incubation.

The starch-casein agar was amended with 50 μg/ml each

of nystatin and cyclohexamide to suppress fungal

growth. The algal population was enumerated on algae

medium of Deft (1988) as modified by Odokuma and

Okpokwasili (1993). The medium was amended with

50 μg/ml each of streptomycin and amphotericin B and

incubation was for seven days. In each of these media,

the different microbial species were counted upon

growth. The different morphotypes of organisms were

subcultured onto freshly prepared medium, stored at

4°C and later identified.

Identification of organisms

The morphological characteristics of the moulds

were macroscopically and microscopically ascertained

using needle mount method and the moulds were

identified according to Larone (1976), Hunter and

Benneth (1973) and Sampson et al., (1984). The yeasts

were characterized biochemically and identified

following the scheme of Laskin and Lechevelier (1977).

The heterotrophic bacteria were identified to generic

level following the scheme of Holt et al., (1994).

The nitrifying bacteria were identified based on the

method used by Colwell and Zambruski (1972).

Nitrogen-fixing bacteria were characterized

biochemically (Smibert and Krieg, 1981) and identified.

Actinomycetes were identified based on the scheme of

Krieg and Holt (1984) and Laskin and Lechevalier

(1977). Identification of algae was based on the scheme

of Fritsch (1975).

RESULTS AND DISCUSSION

The Eagle Island mangrove swamp has been

subjected to various contaminating materials capable of

impairing water and sediment quality. The pH of the

freshwater and mangrove swamp samples showed that

the areas were slightly acidic (Table 1). The pH values

varied from 5.25 ± 0.22 in the non-rhizosphere soil to

6.05 ± 0.33 in the water samples of the mangrove

swamp. In the freshwater swamp, the pH values varied

from 6.51 ± 0.17 in the sediment to 6.88 ± 0.11 in the


Journal of Research in Biology (2012) 2(6): 602-616 604

Table 1: pH values of mangrove and freshwater

samples

Sample pH

Mangrove ecosystem

Rhizosphere soil 5.67 ± 0.16

Non-rhizosphere soil 5.25 ± 0.22

Sediment 5.93 ± 0.32

Water 6.05 ± 0.33

Freshwater ecosystem

Rhizosphere soil 6.88 ± 0.11

Non-rhizosphere soil 6.67 ± 0.21

Sediment 6.51 ± 0.17

Water 6.59 ± 0.19

rhizosphere soil. The mangrove swamp samples were

more acidic than the freshwater samples. The value is

lower than the pH value of seawater and estuaries but is

not unusual for environments like mangrove swamps

(Environmatics, 1995). In a study of Elechi creek, close

to the Eagle Island, a pH range of 6.3 to 7.7 was reported

(Obire et al., 2003). The pH of brackish water bodies

stated by Imevbore (1983) ranged from 6.5 to 7.4.

The pH of brackish New Calabar River water and

sediment were reported, to be 6.40 and 6.62 respectively

(Nweke and Orji, 2009).

The abundance of bacteria, fungi and

actinomycetes in the mangrove and freshwater samples

are shown in Table 2. The population of total aerobic

heterotrophic bacteria ranged from 2.42 (± 0.11) x 104 to

3.06 (± 0.51) x 104 CFU/g or CFU/ml in the mangrove

ecosystem. In the freshwater ecosystem, total aerobic

heterotrophic bacterial count ranged from

4.87 (± 0.71) x 105 to 2.25 (± 0.19) x 106 CFU/g or

CFU/ml. Generally, there were more bacteria, fungi or

actinomycetes in the freshwater samples than in the

mangrove swamp sample. Moreover, sediments

harboured more bacteria than water. Ravikumar (1995)

has made similar observation on Pichavaram mangrove.

This is attributed to nutrient accumulation, precipitation

of inorganic compounds and settlement of dead organic

matter in the sediments. The bacterial counts of the

freshwater samples fell within the range reported for Imo

River, Nigeria (Ihejirika et al., 2011). The bacterial

counts obtained in the mangrove swamp ecosystem are

lower than the counts reported for Elechi creek

(Obire et al., 2005). The occurrence of bacterial

populations followed a particular pattern. Among the

samples, the rhizosphere soil had the highest number of

organisms. Although these counts were lower than those

recorded for the freshwater swamps, the bacterial loads

obtained from the various mangrove samples fell within

the range reported by Austin (1988) in similar

environments. Also, the fungal counts in the mangrove



aV

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s

S.D

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RS

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bacteria =

1.2

6; n

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acteria

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; N

2-fixing

bacteria =

1.5

5; m

ou

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2.6

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0; a

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1.2

3; a

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7

c

Rh

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ete

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ic b

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ria =

1.9

9; n

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bacteria

= 1

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; N

2-fixing

bacteria =

1.1

0; m

ou

lds =

1.3

8; y

easts=

1.6

6; a

lgae =

1.7

4; a

ctino

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s =

1.8

8

Water

Sed

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No

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oil (

NR

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Rhizo

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RS

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Fresh

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Water

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No

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here s

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NR

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Rhizo

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Ma

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Sam

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Ta

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n o

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fresh

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s

4.8

7

0.7

1 x

10

5

8.4

0

2.0

7 x

10

5

1.1

3

0.1

4 x

10

6

2.2

5

0.1

9 x

10

6

2.9

8

0.6

0 x

10

4

2.9

9

0.0

9 x

10

4

2.4

2

0.1

1 x

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4

3.0

6

0

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Hetero

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ic

Bacteria

Co

unts(C

fu

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r C

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a

4.0

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0 x

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4

4.7

3

1.0

6 x

10

4

3.7

3

0.1

5 x

10

4

4.9

7

0.5

0 x

10

4

6.1

0

1.3

1 x

10

3

7.5

1

1.5

8 x

10

3

6.0

6

2.9

5 x

10

3

7.8

2

2

.07

x 1

03

Nitr

ify

ing

1.4

5

0.0

7 x

10

5

1.3

6

0.1

3 x

10

5

1.1

7

0.1

6 x

10

5

1.2

9

0.1

6 x

10

5

1.5

9

0.1

8 x

10

4

1.3

1

0.2

0 x

10

4

1.1

2

0.1

3 x

10

4

1.7

4

0

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x 1

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1.3

7

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x 1

04

1.2

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10

4

1.9

7

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4

2.7

3

0.9

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4.0

2

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2

1.6

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10

2

2.0

1

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10

2

5.3

1

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10

2

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4

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4

1.6

7

0.6

6 x

10

5

2.7

7

0.4

0 x

10

5

5.0

0

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x 1

03

1.2

0

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x 1

04

7.5

2

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x 1

03

1.2

0

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x 1

04

Yeasts

3.2

3

0.2

1 x

10

4

2.7

7

0.2

1 x

10

4

2.3

7

2.2

8 x

10

4

4.1

3

1.4

5 x

10

4

3.0

6

1.4

0 x

10

3

3.2

6

1.0

2 x

10

3

4.8

3

.21

x 1

03

5.9

3

2.2

5 x

10

3

Algae

NIL

5.6

0

2.0

8 x

10

5

2.1

3

0.5

5 x

10

5

4.0

0

2.0

4 x

10

5

NIL

4.5

6

2.6

0 x

10

4

1.0

9

0.3

0 x

10

4

1.6

0

0.3

2 x

10

4

Acti

no

my

cetes

Sam

ple

C

ou

nts

(C

fu/m

l o

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fu/g

)2

B

act

eria

F

un

gi

Alg

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Act

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tes

H

eter

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op

hic

N

itri

fyin

g

N

2-f

ixin

g

M

ou

lds

Yea

sts

Tab

le 2

: T

he

Mic

rob

ial

Pop

ula

tio

n o

f th

e m

an

gro

ve

an

d f

resh

wa

ter

eco

syst

em

s

aV

alu

es a

re m

ean

s of

trip

lica

tes

± S

.D

b R

hiz

osp

her

e ef

fect

(R

S/N

S)

for

het

erotr

op

hic

ba

cter

ia =

1.2

6;

nit

rify

ing

ba

cter

ia =

1.6

4 N

2-

fixin

g b

act

eria

= 1

.55

; m

ou

lds

= 2

.65

; y

east

s =

1.6

0;

alg

ae

= 1

.23 ;

a

ctin

om

yce

tes

= 1

.47

C R

hiz

osp

her

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(R

S/N

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for

het

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op

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ba

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ia =

1.9

9;

nit

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ba

cter

ia =

1.3

3 N

2-

fixin

g b

act

eria

= 1

.10

; m

ou

lds

= 1

.38

; y

east

s =

1.6

6;

alg

ae

= 1

.74 ;

act

inom

yce

tes

= 1

.88

soil is similar to the counts reported for mangrove soil of

Suva, Fiji Islands (Kumar et al., 2007). The occurrence

of higher bacterial count in the rhizosphere soils could be

attributed to edaphic changes induced by plants, which

could influence the proliferation of certain groups of

bacteria. In mangroves, root exudates fuel the microbial

community in sediments (Alongi et al., 1993;

Nedwell et al., 1994). Also mangrove trees can supply

oxygen to the anaerobic subsoil through their aerial roots

and thus remedy the detrimental effects of hydrogen

sulphide in the soil (Sherman et al., 1998; Thibodeau and

Nickerson, 1986). In terrestrial environments, rhizoplane

bacteria induce root exudation, which stimulates

microbial activity by providing bacteria with nutrients

(Lynch and Whipps, 1990).

In this work, soils, sediments and water samples

collected from mangrove and freshwater swamps were

analyzed to determine the types of microorganisms that

inhabit them, their abundance and distribution.

The freshwater samples served as controls. The data

obtained indicate that a wide range of microorganisms

proliferate in the various areas of the swamps in varying

proportions. The ten bacterial genera isolated from the

mangrove swamp belonged to six different families and

they all occurred in the soil. Out of the ten genera, all of

which occurred in the rhizosphere soil, four belonged to

the Enterobacteraceae, two to Nitrobacteraceae and one

each to the Vibrionaceae, Pseudomonadaceae,

Azotobacteraceae and Bacilaceae. In the non-rhizosphere

soil, the same organisms found in the rhizosphere soil

also occurred except for Azotobacter and Bacillus

species. The members of the Enterobacteraceae,

Pseudomonadaceae and Nitrobacteraceae occurred in the

sediment while only genera from Enterobacteraceae and

Bacillaceae families were isolated from the water

samples. From the results presented in Table 3,

Gram negative rods are the dominant organisms in

mangrove swamps whereas in their freshwater

counterpart, there appears to be a balance in the

occurrence of both Gram negative and Gram positive

bacteria. Futhermore, the results implicated Serratia,

Proteus, Aeromonas and Citrobacter species as

indigenous organisms of mangrove swamps since they

did not occur in the freshwater swamps. However, the

occurrence of the same organisms in both environments

could be attributed to the fact that the Eagle Island

mangrove swamp is diurnally flooded by freshwater. In a

bacteriological water quality assessment of Elechi creek,

Citrobacter freundii, Corynebacterium jeikeium,

Escherichia coli, Enterobacter aerogenes,

Flavobacterium balustinum, Proteus mirabilis,

Staphylococcus aureus and Enterococcus faecalis were

isolated. Other bacteria isolated include Pseudomonas,

Aeromonas, Bacillus, Klebsiella, Micrococcus,

Aeromonas and Vibrio species (Obire et al., 2005).

Benka-Coker and Olumagin (1995) have isolated drilling

fluid-ut ilising Staphylococcus, Acinetobacter,

Alcaligenes, Serratia, Clostridium, Enterobacter,

Nocardia, Bacillus, Micrococcus and Pseudomonas

species from mangrove swamp in Niger delta area of

Niger ia. The hydrocarbonoclast ic bacter ia

Staphy lococcus aureus, Bac i l l us cereus ,

Flavobacterium breve, Pseudomonas aeruginosa,

Erwinia amylovora, Escherichia coli, Enterobacter sp.,

Desul fovibrio sp . , Acinetobacter iwof f i i ,

Chromobacterium violaceum, Micrococcus sedentarius,

Corynebacterium sp., and Pseudomonas putrefaciens

were isolated from Iko river mangrove ecosystem,

Nigeria (Udotong et al., 2008). Characterization of

bacterial isolates from Suva mangrove soil revealed

Bacillus as the dominant genera. Other genera such as

Micrococcus, Listeria and Vibrio were also encountered

in soil samples of the Suva mangrove ecosystem

(Kumar et al., 2007). In Pichavaram mangrove, southeast

India, common bacterial genera are Vibrio, Bacillus,

M ic r o co c cu s , P s e ud om o na s , A e r omo n a s,

Flavobacterium etc. (Sathiyamurthy et al., 1990).

Escherichia coli, Micrococcus and Bacillus species have



been isolated from body surfaces of a marine edible

fish Harpodon nehereus of Mumbai coast, India

(Shingadia, 2011).

Bacteria and other microorganisms densely and

ubiquitously colonize freshwater and marine ecosytems.

In these environments, bacteria constitute the primary

agents of early transformation of organic matter and

regeneration of nutrients and also serve as food source

for higher trophic level. By participating in various steps

of the decomposition and mineralization of litter,

sediment microorganisms play essential roles in

mangrove ecosystem and make an important contribution



Bacteria/ Actinomycetesa

Occurrence

Soil

Sediment

Water Rhizosphere Non rhizosphere

Mangrove Ecosystem

Bacteria

Proteus sp. + + + +

Bacillus sp. + – + +

Pseudomonas sp. + + – –

Serratia sp. + + + –

Escherichia coli + + + +

Azotobacter sp. + – – –

Nitrobacter sp. + + – –

Nitrosomonas sp. + + + –

Aeromonas sp. + + – –

Citrobacter sp. + + – +

Actinomycetes

Actinomyces sp. + + + –

Nocardia sp. + – + –

Streptomyces sp. + + + –

Thermoactinomyces sp. + – – –

Freshwater Ecosystem

Bacteria

Klebsiella sp. + + + –

Clostridium sp. + + + –

Corynebacterium sp. + – – –

Pseudomonas sp. + + – –

Listeria sp. + + + –

Bacteriodes sp. + + + –

Nitrosomonas sp. + + – –

Nitrobacter sp. + + – +

Agrobacterium sp. + – – +

Escherichia coli + – – +

Nitrosolobus sp. + – – –

Arthrobacter sp. + + + –

Bacillus sp. – + + +

Azotobacter sp. – + – –

Flavobacterium sp. – + + +

Nitrospira sp. – – + –

Lactobacillus sp. – – – +

Actinomycetes

Streptomyces sp. + + + –

Nocardia sp. + – + –

Actinoplanes sp. + – + –

Actinomyces sp. + + + –

Table 3: Actinomycetes and bacterial population of mangrove swamp and freshwater ecosystems

a +, isolated; –, not isolated

to the productivity of the mangrove ecosystem

(Holguin et al., 2001).

Mangroves provide a unique ecological

environment for diverse bacterial communities. Bacteria

fill a number of niches and are fundamental to the

functioning of these habitats. They are particularly

important in controlling the chemical environment of the

mangal, for instance, nitrogen-fixing bacteria. In this

work, nitrogen-fixing bacteria including species of

Azotobacter and Nitrobacter were isolated from soils of

mangrove and freshwater ecosystems (Table 3). Other

bacterial isolates of the mangrove and freshwater

samples capable of fixing atmospheric nitrogen include

Bacillus, Klebsiella and Clostridium species.

Nitrogen-fixing microorganisms can colonize both

terrestrial as well as marine environments (Sahoo and

Dhal, 2009). Nitrogen-fixing bacteria such as members

of the genera Azospirillum, Azotobacter, Rhizobium,

Clostridium and Klebsiella were isolated from the

sediments, rhizosphere and root surfaces of various

mangrove species (Sengupta and Chaudhuri, 1990;

1991). The possibility of atmospheric nitrogen fixation

by Pseudomonas stutzeri associated with

Languncularia racemosa have been reported (Krotzky

and Werner, 1987; Alongi et al., 1992; 1993).

Pseudomonas species are among the most widely

distributed bacteria. In this study, Pseudomonas species

was isolated from soils of both freshwater and mangrove

ecosystems. Another noteworthy bacterium is Bacillus

species, that is isolated from the soils, sediments and

riverwaters of freshwater and mangrove swamp

ecosystems. Bacillus species exhibit phosphatase

activity, capable of solubilizing phosphate. In an arid

Mexican mangrove ecosystem, bacterial strains including

Bacillus amyloliquefaciens and Bacillus licheniformis

were isolated from black and white mangroves

(Vazquez et al., 2000).

Species of actinomycetes belonging to the

famil ie s Act ino mycetaceae, Nocard iaceae,

Streptomycetaceae, Micromonosporaceae and the

coryneform group of bacteria were isolated only from

soil and sediment samples of the mangrove and

freshwater swamps. No species of actinomycetes was

obtained from the water samples. The occurrence of

actinomycetes in soils and sediments has been reported

by Takizawa et al., (1993). The freshwater soils habour

more actinomycetes than mangrove sediment. This

corroborated the report of Goodfellow and Williams

(1983), that the actinomycetes population density is less

common in marine sediments relative to terrestrial soils.

The isolation of a member of the Micromonosporaceae

and Streptomycetaceae in this work agrees with the

reports of Watson and Williams (1974), that

Micromonosporaceae constitute the dominant

actinomycetes in beach sand and Jensen et al., (1991)

that Streptomycetes are the predominant species at

shallow depths in near shore tropical marine

environments. Actinomycetes belonging to the family

Streptomycetaceae was also found to dominate in the

environmental samples from the sediments at coastal and

offshore area of Nagasaki, Japan (Anzai et al., 2008).

Micromonosporaceae have been found to be the

dominant actinomycetes group in a range of aquatic

environments, particularly in the deeper mud layers as

well as in deep sea sediments (Mincer et al., 2002).

Thus, Thermoactinomyces and Streptomyces are by this

work proffered as autochthonous members of the

mangrove swamp of the Eagle Island. The population of

actinomycetes obtained from the sediments and soils in

this work is slightly higher than those recorded by

Weyland (1969) and Okami and Okazaki (1978) in

coastal sediments but agrees with the figures of

Takizawa et al., (1993). Similarly, there are reports of

the occurrence of actinomycetes in terrestrial soils

(Nolan and Cross, 1988), thus buttressing their isolation

in mangrove soils in this work. One interesting aspect of

the result presented in Tables 2 and 3 is the absence of

actinomycetes in the water samples. This might suggest




609 Journal of Research in Biology (2012) 2(6):602-616

Fungia

Occurrence

Soil

Sediment


Mangrove Ecosystem

Moulds

Aspergillus niger + + + +

Aspergillus flavus + – + –

Aspergillus ochraceus + + – +

Rhizopus stolonifer + + + –

Mucor hiemalis + + + +

Fusarium verticilloides + + + +

Fusarium moniliforme + + + +

Fusarium oxysporum + + – +

Botyritis cinerea + + – –

Trichoderma viride + + – –

Verticillium lecanii + + + –

Penicillium caseicolum + + + –

Penicillium brevicompactum + + + –

Penicillium digitatum + + + +

Geotrichum candidum + + + +

Sterilia mycelia + – – –

Yeasts

Candida sp. + + + +

Pichia sp. + + + –

Saccharomyces sp. + + + +

Kluveromyces sp. + + + –

Trigonopsis sp. + + + +

Rhodospirillum sp. + + + +


Moulds

Aspergillus niger + + + +

Aspergillus flavus + + + –

Aspergillus ochraceus + – – –

Penicillium brevicompactum + + – –

Penicillium expansum + + + +

Penicillium digitatum + – – -

Trichoderma harzianum + – + +

Monascus rubber + + – –

Verticillium trifidum + + + –

Byssochlamys nivea + + + –

Chalaropsis sp. + + – –

Phialophora hoffmanii + – – –

Trichothecium roseum + + – –

Fusarium oxysporum + + + +

Fusarium solani + – – –

Aureobasidium pullulans + + – –

Bdellospora helicoides + – – –

Chrysonilia sitophila + – – –

Yeasts

Candida sp. + + + +

Saccharomyces sp. + – – –

Schizosaccharomyces sp. + + – –

Saccharomycopsis sp. + – – –

Yarrowia sp. + – – –

Kluveromyces sp. + + + –

Brettanomyces sp. + + – –

Zygosaccharomyces sp. + – – –

Table 4: Fungal population of mangrove swamp and freshwater ecosystems


that they are unable to survive in brackish water habitats

such as those found in the mangrove swamps of the

Niger Delta. While high counts of bacteria and

actinomycetes were expected in environments such as

this, the relatively low counts (excepts for the sediments)

obtained could be attributed to the harsh conditions

presented by regular mixing of fresh and seawater which

ultimately create an environment with a wide range of

continually fluctuating conditions which may be

unfavourable for bacterial colonization. Furthermore, the

higher actinomycete population is expected, since it is

known that actinomycetes do better than most bacteria in

such stressed environments (Kobayashi and Rittman,

1982).

The result presented in Table 4 shows that from

the mangrove swamp, 16 species of fungi belonging to

several groups especially the ascomycetes were isolated.

More species were isolated from the freshwater swamp.

This agrees with the report that fungi are poorly

represented in marine environments, since the marine

fungi account for only 5% of the total fungal flora

(Purushothaman and Jayalakshmi, http://ocw.unu.edu).

The lower counts of fungi (Table 2) in mangrove than in

freshwater ecosystem also buttressed this fact. In this

work, the most frequently encountered fungi were

Aspergillus and Penicillium species, which occurred on

virtually all the areas sampled. The predominance of

Aspergillus and Penicillium in Pichavaram mangrove,

southeast India has been reported (Mohamed- Salique et

al., 1985; Venkatesan and Natarajan, 1986). Fungi

identified as Alternaria maritima, Aspergillus flavus,

A sperg i l l u s niger , A sperg i l l u s sul fu rus ,

Aureobasidium pullulans, Bispora sp., Cladosporium sp.,

Humicola sp., Mucor sp., Penicillium sp., Phoma sp.,

Pythium sp. and Rhizopius sp. were isolated from black

mangrove (Avicennia marina) growing in Korangi creek

and Clifton areas of Karachi, Pakistan (Mehdi and

Saifullah, 1992). This report shows the occurrence of

Aspergillus, Trichoderma, Mucor, Fusarium,

Verticillium, Botrytis and Penicillium species as

inhabitants of mangrove swamps. The rhizosphere soil

had more organisms than any other area. Other

prominent group isolated in this work was oomycetes.

Similar results by Fell et al., (1980) suggest that fungi

particularly the oomycetes play a substantial role in the

breakdown of mangrove litter. Total heterotrophic mould

counts (Table 2) revealed higher values for the

freshwater than the mangrove swamp. However, the

counts in mangrove swamp agreed with those reported

by Odokuma and Okpokwasili (1993) in a Niger Delta

brackish water ecosystem.

Species of yeasts belonging to the Ascomycotina,

Basidiomycotina and Deuteromycotina were isolated

from the mangrove swamp in this study. These yeasts

were found in the soil, sediment and water samples.

However, there were greater diversity of yeast in soil

samples than in the sediment and water samples from

mangrove and freshwater ecosystems. The results

(Table 2) also showed that the rhizosphere soil harboured

more yeasts than the other areas. The presence of

nutrients from root exudates may have accounted for

higher yeast load in the rhizosphere. It appears that

Rhodospiridium, Trigonopsis and Pichia species are

natural inhabitants of mangrove swamps. Candida and

Kluveromyces species were widely distributed in the

mangrove and freshwater ecosystems. In a Brazilian

mangrove ecosystem, Kluyveromyces aestuarii

predominated the ascomycetous yeast communities of

detritus feeding crabs (Araujo et al., 1995).

In the algal composition of the mangrove swamp,

20 species were isolated of which the Cyanophyceae had

higher number of taxa, followed by Bacillarophyceae,

Chlorophyceae, Chrysophyceae, Euglenophyceae,

Phaeophyceae, Cho lo rococcaceae and the

Xanthophyceae. Species belonging to the above families

were also isolated from the freshwater habitat. This result

is similar to the results of Chindah (1988) and Chindah

and Pudo (1991) on the algal composition found in the





Algaea

Occurrence

Soil

Sediment


Mangrove Ecosystem

Chlamydomonas chrenbergi – + + +

Nostoc sp. – – + +

Protococcus viridis + + – +

Euglena gracilis – – – +

Euglena acus – – – +

Borgea plantonica – – – +

Synura uvella – – – +

Oscillatoria tenium – – – +

Spirogyra adnata – – – +

Spirulina maior – – – +

Laminaria sp. – – – +

Denticula valida – – + +

Gleocapsa quarternata – – – +

Fischerella sp. + + – –

Chlorobotrys regularis + – – –

Gomphonema olivaceum + – – –

Asterionella gracillima + + – –

Asterionella formosa + – – –

Vaucheria sessilis – – + –

Chromulina nebulosa – – + –


Oscillatoria redeki – – – +

Chromulina zartensis – – + +

Synedra ulna – + – +

Ochromonas mutabilis – – – +

Ankistrodesmus septatus – – – +

Chlamydomonas angulosa – – + +

Chlamydomonas elegans – – – +

Chlamydomonas grandis – – – +

Chlamydomonas pertusa – – – +

Spirogyra mirabilis – – – +

Pinularia viridis + – + +

Cosmasium birretum – – + +

Euglena acus + – + +

Amphora ovalis – – + +

Chlorella variegata – – – +

Urothrix oscillatoria + + – +

Enteromorpha compressa + – – +

Stuarastrum tumidum + + – +

Scenedesmus acuminatus – – – +

Cymbella cistula + + – –

Ovulites margaritula + + – –

Coscinodiscus excentricus + – – –

Denticula valida + – – –

Oscillatoria redeki – + + –

Navicula pelliculosa – – + –

Euastrum didelta – – + –

Botrydiopsis arrhiza – – + –

Chloromeson agile – – + –


Table 5: Algal population of mangrove swamp and freshwater ecosystems



Bonny River. The result shown in Table 2 indicates that

the rhizosphere soil had highest population of algae than

non-rhizosphere soil, sediment or water and that more

populations occurred in the freshwater than in the

mangrove swamp. However, in terms of diversity, more

species were isolated from the water samples. These

species live mostly in the upper parts of the water

column where they are well positioned to trap solar

energy, thereby contributing a sizeable proportion of the

net primary productivity in the ecosystem. From the

results, it can be reasoned that Gomphonema olivaceum,

Chlamydomonas ehrenbergii, Laminaria sp.,

Spirulina maior, Fischerella sp., Asterionella spp.,

Borgea plantonica, Nostoc sp., Chlorobotrys regularis

and Vaucheria sessilis are typical of mangrove swamps.

Generally, the occurrence of diverse microbial

species in mangrove swamps has been established.

However their distributions in different areas were not

uniform. In most cases (except for the algae in water and

actinomycetes in sediments), the rhizosphere area of the

soil had the greatest number and diversity of species.

This report suggests that mangrove and freshwater

ecosystems provide shelter and nurturing sites for many

microorganisms. The study of microbial diversity in

these environments is vital to the understanding of the

processes of the natural media, which may present potent

novel microorganisms for screening of bioactive

compounds.

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